1. Field of the Invention
The present invention relates to image processing apparatus and method which perform processing concerning color matching, and a storage medium.
2. Related Background Art
A color matching method is the method to match tints of two devices (e.g., a monitor and a color printer each having a different color reproduction range) with each other. When the color reproduction range of the monitor is compared with the color reproduction range of the color printer, the color reproduction range of the monitor is generally wider than the color reproduction range of a printing output by the color printer, whereby a part of colors represented by the monitor can not be reproduced by the printer.
Thus, various methods to realize color matching between the monitor and the color printer are designed. Concretely, in these methods, in a device-independent uniform color space such as CIE-L*a*b* color system, color gamut mapping (or color space compression) to the color reproduced by the monitor is performed to obtain the color reproducible by the printer, thereby realizing the color matching between the monitor and the color printer.
As a conventional color matching method, there is designed a method which performs compression processing without dislocating hue angles as shown in FIG. 18, a method which performs compression processing at equal value (lightness) as shown in FIG. 19, and a method which performs compression processing toward one specific point on an achromatic color axis as shown in FIG. 20, or the like.
In an actual processing system, when image data is subjected to color gamut mapping pixel by pixel, an enormous processing time is necessary. Thus, a multidimensional table in which only representative points were subjected to the color gamut mapping is previously generated, and colors at points other than the representative points are subjected to color processing according to multidimensional interpolation processing.
However, in the above conventional case, since the color matching is performed in the device-independent L*a*b* color space, it is impossible to realize color matching in consideration of how to use inks dependent on a printer (device).
Further, in such the conventional color gamut mapping as shown in FIG. 18, in the case where the compression is performed without dislocating the hue angles in an a*b* plane, since the uniform color space such as the L*a b* color space does not completely reflect a human's sight characteristic, there is a problem that an appeared tint rather changes because the compression is performed without dislocating the hue angle. As to value (lightness) compression, in the case where the compression is performed at the identical lightness as shown in FIG. 19, there is an advantage that the brightness itself is maintained. However, there is a problem that a chroma of a highlight area or a shadow area disappears extremely. Further, in the case where the lightness compression is performed in such the manner as shown in FIG. 20, the reproducibility of the chroma improves in comparison with the compression method shown in FIG. 19. However, there is a problem that unbalance of the lightness occurs due to the hue, whereby feeling of wrongness appears in reproduction image quality.